Canada Thistle

cthistleCanada Thistle is a very aggressive noxious weed. It is extremely hardy and difficult to get rid of, leading to many County residents having this invasive weed in their backyards and fields.


Plant Description 

  • Spiny green leaves that alternate along the stem
  • Leaves are irregularly lobed with sharp spines
  • Stems are hollow and usually smooth
  • Flowers range from white to purple
  • Mature plant height ranges from 30 to 180cm



Facts on Canada Thistle 

  • There are approximately 5,000 seeds per plant
  • Seeds can remain viable in the soil for up to 20 years
  • Canada Thistle causes greater crop loss than any other broadleaf weed in Western Canada
  • Creeping perennial that begins growth in the early spring


Methods of Control 

  • The best control option is to stop the plant from going to seed
  • Combining control methods is the best way to manage this weed
  • Maintain desirable plants in the area that are able to  outcompete the Canada Thistle
  • Mowing can be effective if combined with a herbicide treatment (see Crop Protection Guide)
  • Exercise proper crop rotation